c++: Replace "C++2a" with "C++20".

C++20 isn't final quite yet, but all that remains is formalities, so let's
go ahead and change all the references.

I think for the next C++ standard we can just call it C++23 rather than
C++2b, since the committee has been consistent about time-based releases
rather than feature-based.

gcc/c-family/ChangeLog
2020-05-13  Jason Merrill  <jason@redhat.com>

	* c.opt (std=c++20): Make c++2a the alias.
	(std=gnu++20): Likewise.
	* c-common.h (cxx_dialect): Change cxx2a to cxx20.
	* c-opts.c: Adjust.
	* c-cppbuiltin.c: Adjust.
	* c-ubsan.c: Adjust.
	* c-warn.c: Adjust.

gcc/cp/ChangeLog
2020-05-13  Jason Merrill  <jason@redhat.com>

	* call.c, class.c, constexpr.c, constraint.cc, decl.c, init.c,
	lambda.c, lex.c, method.c, name-lookup.c, parser.c, pt.c, tree.c,
	typeck2.c: Change cxx2a to cxx20.

libcpp/ChangeLog
2020-05-13  Jason Merrill  <jason@redhat.com>

	* include/cpplib.h (enum c_lang): Change CXX2A to CXX20.
	* init.c, lex.c: Adjust.

1 files changed, 14 insertions, 14 deletions

diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
index 58ba094..bd617d3 100644
--- a/gcc/c-family/c-opts.c
+++ b/gcc/c-family/c-opts.c
@@ -112,7 +112,7 @@ static void set_std_cxx98 (int);
 static void set_std_cxx11 (int);
 static void set_std_cxx14 (int);
 static void set_std_cxx17 (int);
-static void set_std_cxx2a (int);
+static void set_std_cxx20 (int);
 static void set_std_c89 (int, int);
 static void set_std_c99 (int);
 static void set_std_c11 (int);
@@ -636,10 +636,10 @@ c_common_handle_option (size_t scode, const char *arg, HOST_WIDE_INT value,
 	set_std_cxx17 (code == OPT_std_c__17 /* ISO */);
       break;
 
-    case OPT_std_c__2a:
-    case OPT_std_gnu__2a:
+    case OPT_std_c__20:
+    case OPT_std_gnu__20:
       if (!preprocessing_asm_p)
-	set_std_cxx2a (code == OPT_std_c__2a /* ISO */);
+	set_std_cxx20 (code == OPT_std_c__20 /* ISO */);
       break;
 
     case OPT_std_c90:
@@ -925,11 +925,11 @@ c_common_post_options (const char **pfilename)
   /* -Wcomma-subscript is enabled by default in C++20.  */
   SET_OPTION_IF_UNSET (&global_options, &global_options_set,
 		       warn_comma_subscript,
-		       cxx_dialect >= cxx2a && warn_deprecated);
+		       cxx_dialect >= cxx20 && warn_deprecated);
 
   /* -Wvolatile is enabled by default in C++20.  */
   SET_OPTION_IF_UNSET (&global_options, &global_options_set, warn_volatile,
-		       cxx_dialect >= cxx2a && warn_deprecated);
+		       cxx_dialect >= cxx20 && warn_deprecated);
 
   /* Declone C++ 'structors if -Os.  */
   if (flag_declone_ctor_dtor == -1)
@@ -1021,9 +1021,9 @@ c_common_post_options (const char **pfilename)
   if (flag_sized_deallocation == -1)
     flag_sized_deallocation = (cxx_dialect >= cxx14);
 
-  /* char8_t support is new in C++2A.  */
+  /* char8_t support is new in C++20.  */
   if (flag_char8_t == -1)
-    flag_char8_t = (cxx_dialect >= cxx2a);
+    flag_char8_t = (cxx_dialect >= cxx20);
 
   if (flag_extern_tls_init)
     {
@@ -1045,11 +1045,11 @@ c_common_post_options (const char **pfilename)
   if (warn_return_type == -1 && c_dialect_cxx ())
     warn_return_type = 1;
 
-  /* C++2a is the final version of concepts. We still use -fconcepts
+  /* C++20 is the final version of concepts. We still use -fconcepts
      to know when concepts are enabled. Note that -fconcepts-ts can
      be used to include additional features, although modified to
      work with the standard.  */
-  if (cxx_dialect >= cxx2a || flag_concepts_ts)
+  if (cxx_dialect >= cxx20 || flag_concepts_ts)
     flag_concepts = 1;
   else if (flag_concepts)
     /* For -std=c++17 -fconcepts, imply -fconcepts-ts.  */
@@ -1724,9 +1724,9 @@ set_std_cxx17 (int iso)
 
 /* Set the C++ 202a draft standard (without GNU extensions if ISO).  */
 static void
-set_std_cxx2a (int iso)
+set_std_cxx20 (int iso)
 {
-  cpp_set_lang (parse_in, iso ? CLK_CXX2A: CLK_GNUCXX2A);
+  cpp_set_lang (parse_in, iso ? CLK_CXX20: CLK_GNUCXX20);
   flag_no_gnu_keywords = iso;
   flag_no_nonansi_builtin = iso;
   flag_iso = iso;
@@ -1734,8 +1734,8 @@ set_std_cxx2a (int iso)
   flag_isoc94 = 1;
   flag_isoc99 = 1;
   flag_isoc11 = 1;
-  /* C++2a includes concepts. */
-  cxx_dialect = cxx2a;
+  /* C++20 includes concepts. */
+  cxx_dialect = cxx20;
   lang_hooks.name = "GNU C++17"; /* Pretend C++17 until standardization.  */
 }